A Nyquist-rate adaptation algorithm for fractionally spaced equalizers

Abstract

Fractionally spaced equalizers have attained popularity because of their notable advantages, chiefly an ability to form an optimal linear receiver and provide performance quite insensitive to receiver timing phase. This work describes a time-domain Nyquist-rate algorithm that broadens the utility of fractional equalizers by permitting least-mean-square or true zero-forcing adaptation, more rapid convergence relative to synchronous coefficient updating, user specification of the end-to-end Nyquist channel, and elimination of the coefficient drift phenomenon. The investigation includes an analytical description of the algorithm, a functional circuit architecture, and reference to a computer simulation illustrating stable equalizer operation in the presence of dispersion on a digital subscriber loop.